The Recycling Oceania Technical Library brings together articles, technical information, research and firsthand accounts relating to Subcritical Water (SCW) processing technology.
The purpose of this library is to help waste operators, engineers, researchers, councils and other interested parties understand the technology, its commercial history in Japan and its potential applications in New Zealand and Oceania. Materials include technical explanations, interviews with the inventor, information from Japanese commercial installations and discussions of waste treatment, resource recovery and energy production.
We welcome technical questions, independent evaluation and constructive discussion. As additional research and testing results become available, this library will continue to develop.
Subcritical Water Processing – Full English/Japanese Technical Review
Comprehensive Technical Documentation (213 Pages)
This extensive technical reference provides detailed background information on Subcritical Water (SCW) processing technology developed in Japan. Intended for engineers, researchers, waste-management professionals and local authorities, it provides a deeper technical resource than the introductory material elsewhere on this website. The document supports further investigation into the principles, development and potential industrial applications of SCW technology.
Technical note: This reference is not a New Zealand-specific engineering design or independently verified performance assessment. Proposed applications require appropriate feedstock testing, engineering evaluation and regulatory assessment.
Download the Full English/Japanese Technical Review (PDF)
Subcritical Water Processing of Organic Waste and Wastewater Sludge
Technical Discussion Paper | September 2026
This technical discussion paper examines the potential application of Subcritical Water (SCW) technology to wastewater sludge and other organic-based residual waste streams in New Zealand. Drawing on more than 20 years of Japanese commercial experience, independent scientific research and current developments in hydrothermal processing, the paper explores opportunities for substantial waste reduction, resource recovery and improved contaminant management.
Topics include the treatment of wastewater sludge, transformation of organic contaminants, the behaviour of PFAS and heavy metals, recovery of carbon-rich char, and the potential integration of SCW with additional treatment technologies. The paper also examines Japanese sludge-processing experience and outlines a practical pathway for independent testing of New Zealand waste streams before considering commercial implementation.
Potential Applications of Subcritical Water Technology for Hazardous and Industrial Waste
Technical and Commercial Opportunity Assessment | October 2026
This discussion paper examines the potential application of Subcritical Water (SCW) technology to selected hazardous and industrial waste streams in New Zealand.
Drawing on observations from the New Zealand waste industry and technical information provided by SCW developer Mr Kaneo Ishimori, the paper explores opportunities to treat difficult organic waste materials that are currently stabilised, landfilled or exported for specialist treatment.
Particular attention is given to chlorinated organic compounds, oily waste, contaminated absorbents, industrial sludges and polymer-based chemical residues.
The paper also considers opportunities for integrating hazardous waste treatment with existing construction and demolition waste processing operations.
Proposed applications remain subject to independent testing, contaminant analysis and regulatory assessment.
Download Technical Discussion Paper (PDF – 11 pages)
PVC and Subcritical Water Processing – Chemistry, Chlorine Management and Commercial Experience
PVC presents particular challenges in waste processing because of its high chlorine content. When heated, PVC can release hydrogen chloride (HCl), creating potentially corrosive conditions that must be carefully managed. This bilingual technical discussion paper (English and Japanese) explains the chemistry of PVC decomposition, the theoretical quantities of hydrochloric acid produced, and how alkaline materials can help neutralise acidity. It also examines practical feedstock management, reactor maintenance, chlorine distribution and process-water treatment.
Importantly, according to technology developer Kaneo Ishimori, commercial SCW facilities in Japan have processed PVC-containing mixed waste for more than 20 years, with no significant PVC-related operating problems reported. The paper combines established chemistry, published research and Japanese commercial experience, while identifying areas where further technical information and independent testing will be valuable.
Technical Discussion Paper | October 2026 | 13 pages | English / Japanese
Technical Articles and Explanations (Click any title to open)
Recycling Oceania publishes articles explaining the science, engineering and practical applications of Subcritical Water processing. These cover operating principles, waste reduction, energy recovery, environmental considerations and the opportunities for applying Japanese commercial experience in New Zealand.
A selection of articles are available below with others accessible here: Rod Hellyer | Substack
SCW Technical Overview
Description: An introduction to Subcritical Water processing, explaining how elevated temperature and pressure can transform waste materials, reduce disposal volumes and recover potentially useful resources. The article also discusses the technology’s commercial development in Japan.
Waste Worth by the Numbers
Description: What happens when we stop looking at waste simply as something to dispose of and start considering its potential value? This article examines the quantities of waste currently sent to landfill, the potential for SCW processing to reduce disposal volumes, and the energy that could be recovered from the resulting char. Using illustrative New Zealand examples, it explores how waste management could become an opportunity for resource and energy recovery.
What a Steam Train Taught Me About SCW
Description: Sometimes the simplest way to understand a complex technology is through something familiar. Inspired by a journey along New Zealand’s Old Coach Road, this article uses the principles of steam power to explain how Subcritical Water processing works — and why temperature and pressure can transform waste materials into potentially useful resources.
The Carbon May Be Ancient. The Waste Isn’t.
Description: What happens to the carbon contained in waste when we recover it as a useful fuel? This article explores the distinction between fossil-derived and biogenic carbon, the potential role of Subcritical Water processing in resource recovery, and how carbon capture and storage might fit into future waste-to-energy systems.
We Clean the Water. But What Do We Do With the Sludge?
Description: Wastewater treatment produces cleaner water, but it also leaves behind large quantities of sewage sludge that must be managed. This article examines the challenges of sludge disposal, the limitations of conventional treatment methods, and how Subcritical Water processing could offer an alternative. It also looks at commercial experience in Japan and the potential opportunities for New Zealand wastewater operators.
Technical Concepts and Future Development…
In addition to established commercial SCW applications, Recycling Oceania is exploring opportunities to integrate complementary technologies and develop new waste-treatment solutions. These concepts are presented to encourage technical discussion, independent evaluation and potential collaboration with researchers, engineers and industry partners.
Conceptual Technical Overview — SCW/SCWO
Description: This article explores the potential integration of Subcritical Water (SCW) processing with Supercritical Water Oxidation (SCWO). The concept combines SCW’s ability to transform solid waste and recover useful materials with SCWO’s potential to treat difficult organic contaminants in liquid waste streams. Together, these technologies could offer a more comprehensive approach to waste treatment, particularly for sewage sludge and contaminated industrial materials. The proposed combination remains a conceptual development requiring engineering evaluation and testing.
Technical Enquiries and Collaboration
Recycling Oceania welcomes enquiries from engineers, researchers, waste operators, councils and industry partners interested in evaluating Subcritical Water processing technology. We are particularly interested in independent testing, technical discussion and identifying practical applications where the technology could deliver measurable environmental and commercial benefits. If you would like to discuss a particular waste stream, review technical information or explore a potential project, please contact Recycling Oceania.